Science, Tech, Math › Science Temperature Definition in Science Can You Define Temperature? Share Flipboard Email Print nikamata/Getty Images Science Chemistry Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated May 09, 2019 Temperature is the property of matter which reflects the quantity of energy of motion of the component particles. It is a comparative measure of how hot or cold a material is. The coldest theoretical temperature is called absolute zero. It is the temperature where the thermal motion of particles is at its minimum (not the same as motionless). Absolute zero is 0 K on the Kelvin scale, −273.15 C on the Celsius scale, and −459.67 F on the Fahrenheit scale. The instrument used to measure temperature is a thermometer. The International System of Units (SI) unit of temperature is the Kelvin (K), although other temperature scales are more commonly used for everyday situations. Temperature may be described using the Zeroth Law of Thermodynamics and the kinetic theory of gases. Temperature Scales There are several scales used to measure temperature. Three of the most common are Kelvin, Celsius, and Fahrenheit. Temperature scales may be relative or absolute. A relative scale is based on the kinetic behavior relative to a certain material. Relative scales are degree scales. Both the Celsius and Fahrenheit scales are relative scales based on the freezing point (or triple point) of water and its boiling point, but the size of their degrees are different from each other. The Kelvin scale is an absolute scale, which has no degrees. The Kelvin scale is based on thermodynamics and not on the property of any specific material. The Rankine scale is another absolute temperature scale.